A.W. Tozer addresses the challenge of unbelief, emphasizing that our struggle often stems from an inability to visualize certain spiritual truths rather than a lack of faith. He points out that while we easily believe in historical biblical events due to their external nature, concepts like regeneration and divine indwelling are harder to grasp because they are internal and abstract. Tozer encourages believers to recognize this psychological barrier and not to blame themselves for their struggles with faith. He asserts that understanding this distinction can help alleviate the guilt associated with unbelief.